Various types of automatic brake slack adjusting or brake clearance adjusting mechanisms are known in the art. In general, they have characteristically been complicated in design and expensive to manufacture. Examples of adjusters that utilize a pawl to rotate a nut that in turn advances a piston to maintain desired disengaged clearance between a brake shoe and a surface such as a wheel rotor to be braked are respectively disclosed in U.S. Pat. Nos. 3,949,840 and 3,966,028, the disclosures of all which are incorporated herein by reference. An example of a brake adjusting mechanism of complex design that utilizes a pawl and toothed ring to provide automatic adjustment of brake clearance is disclosed in U.S. Pat. No. 4,064,973, the disclosure of which is incoporated herein by reference. An example of a brake adjuster that utilizes a complicated worm and worm gear arrangement to adjust clearance between a brake shoe and an object to be braked is disclosed in U.S. Pat. No. 4,088,206, the disclosure of which is incorporated herein by reference. An example of an automatic slack adjuster that utilizes a gear and rack arrangement in conjunction with a clutch is diclosed in U.S. Pat. No. 4,019,612, the disclosure of which is incorporated herein by reference. None of the above, however, disclose or suggest a simplified means by which to automatically maintain a desired clearance between a brake shoe lining and an object to be frictionally braked by the lining that is inexpensive to manufacture.
Heretofor, brake clearance adjusters have been unable to utilize the full stroke or travel of the driving piston or cylinder requiring high precision and high cost components to provide an adjuster motion that is characteristically some fraction of the piston motion whereas the brake adjustment assembly of the present invention features the use of lower cost components having broader tolerances which, due to its simple and unique design, is able to utilize directly the travel distance of the driving piston or cylinder to characteristically provide a more favorable adjuster motion to lining clearance ratio which advantageously reduces the precision required for the adjustment mechanism.